In a railway vehicle, each motorized bogie is provided with means for driving each axle in rotation. The drive means comprise at least one motor, at least one reducing gear, and a mechanical device for transmitting the driving torque of the motor to the axle and for transmitting the braking torque of the axle to the motor, while permitting relative movements between the motor and the axle induced by the primary suspensions. The drive means differ in the distribution of their masses, which are either “non-suspended”, that is to say connected to the axle, or “suspended”, that is to say connected to the bogie chassis above the primary suspensions. The drive means differ in their ease of integration into the bogie in terms of space requirement, either by width (that is to say parallel to the axle shaft) or by length (parallel to the direction of travel of the vehicle). They differ in complexity by the number of components they contain.
In order to reduce vertical stresses on the track, it is advantageous to reduce the non-suspended masses. In order to facilitate integration of the drive means, it is advantageous to reduce the space requirements.
The drive known as a “semi-suspended motor” conventionally comprises a motor which rests oscillating on the axle by two bearings and to which there is fixed a reducing gear box. The motor output gear engages with a wheel fixed to the axle. An articulated reaction rod allows the torques to be absorbed and displacements due to movements between the bogie chassis and the axle to be ensured. This transmission is simple to implement but has high non-suspended masses, which limits the speed of the vehicle.
In the so-called “hollow shaft” drive, the reducing gear and the motor are rigidly connected and are fixed to the bogie chassis. The torques are transmitted between the output bearing of the reducing gear and the axle by a hollow-shaft device, which also ensures displacements due to movements between the bogie chassis and the axle. This transmission increases the space requirement of the bogie in the direction of travel of the vehicle. The space occupied by the hollow shaft on the axle also requires the addition of an intermediate wheel to the reducing gear. This solution allows the vehicle to travel at high speeds but it is complex to implement because it requires a hollow bearing at the output of the reducing gear, connections between that bearing and the hollow shaft on the reducing gear side as well as between the axle and the hollow shaft.
The “semi-suspended reducing gear” drive is a compromise between the above two types of drive in terms of non-suspended masses and complexity. The motor is fixed to the bogie chassis and the reducing gear is on the one hand fixed pivotably to the axle and on the other hand is connected to the bogie chassis by a reaction rod. A mechanical coupling connects the motor shaft to the input bearing of the reducing gear and ensures displacements between the motor output and the input of the reducing gear, which displacements are due to the suspensions.
In railway vehicle bogies, the axles of the bogie are generally connected by an “exterior” chassis, in which the side members are arranged outside the wheels, or by an “interior” chassis, in which the side members are arranged inside the wheels, that is to say between the wheels, on axle boxes which are likewise arranged inside the wheels.
The interior chassis enables the mass of the bogie to be lowered and its manufacturing costs to be reduced. Such a chassis also allows the brake callipers to be accommodated outside the chassis, which improves the accessibility of the callipers should they have to be removed, and also improves the accessibility of the wheels. In the case of a power bogie having an interior chassis, there is little space in the transverse direction to accommodate a powerful and bulky motor. The only solution of the prior art which allows a powerful motor, and the associated transmission, to be accommodated, while limiting the non-suspended masses, is hollow-shaft suspension, which is complex to implement, as described above.